Rake db:migration error from Book

Hi,

Right now I am working on the application given from the book

Pragmatic.Bookshelf.Agile.Web.Development.with.Rails.2nd.Edition.Dec.2006

On page 80. I have done the rake db:migrate on the code…

class AddPrice < ActiveRecord::Migration
def self.up
add_column :products, :price, :decimal, :precision => 8, :scale => 2,
:default => 0
end
def self.down
remove_column :products, :price
end
end

When we do rake db:migrate it results in error…

Microsoft Windows XP [Version 5.1.2600]
© Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\Sharma>cd
c:\radrails_projects\depotaugust152007

C:\radrails_projects\depotaugust152007>rake db:migrate
(in C:/radrails_projects/depotaugust152007)
== AddPrice: migrating

– add_column(:products, :price, :decimal, {:default=>0, :precision=>8,
:scale=>
2})
rake aborted!
You have a nil object when you didn’t expect it!
You might have expected an instance of Array.
The error occured while evaluating nil.[]

(See full trace by running task with --trace)

C:\radrails_projects\depotaugust152007>

Please suggest me the ways to solve this…

Thanks in advance sharma